ELECTRON-MICROSCOPIC EVIDENCE OF A VIRAL NATURE FOR OSTEOCLAST INCLUSIONS IN PAGETS-DISEASE OF BONE

Circumstantial evidence from electron microscopic and immunological st udies support the view that Paget's disease of bone represents a slow virus infection. However, there is only limited information available regarding its electron microscopic, enzyme and immunocytochemical char acteristics. Two cases were studied using electron microscopy with par ticular emphasis on the inclusions in osteoclasts. Detailed ultrastruc tural and cytochemical studies including immune-electron microscopy we re performed. Some osteoclasts demonstrated specific virus-like struct ures composed of aggregations of microtubules in the nucleus and cytop lasm. The structures were easily digested by trypsin or protease, and were sensitive to RNase, which provided substantial evidence of a prot einaceous nature and inclusion of ribonucleic acid. Immunocytochemical examination identified binding of anti-respiratory syncytial virus an d anti-measles virus antibodies in the tissue obtained from one of the two cases examined. The presence of viral antigens in structures in t he cytoplasm of Pagetic osteoclasts supports the theory of paramyxovir us involvement in this disease.